The protesters have demanded that Hong Kong authorities stop to ignore negative effects that parallel trading has on the economy of Sheung Shui, an area close to the border with mainland China, the RTHK broadcaster has reported.
The Hong Kong police said a series of clashes had occurred during the protest, calling on the demonstrators to end violence and disperse.
"The Hong Kong police is calling on the participants of the protest to end violent actions and disperse as quickly as possible," the police statement read.
Parallel traders buy goods tax-free in Hong Kong to resell them in mainland China. This causes shortages of household goods, medicines, infant formula and some other daily necessities. Multiple entry visa policy allows parallel traders to cross the border many times and export goods from Hong Kong frequently.
Saturday's protest follows a series of demonstrations in Hong Kong over a controversial extradition bill that would have allowed people arrested in the former UK colony to be sent for trial in mainland China. Hong Kong leader Carrie Lam said earlier this week that the bill was "dead."